Pulse generator employing resonant lc network in base-emitter circuit of transistor



Dec. 19, 1967 w. J. JONES 3,359,430

PULSE GENERATOR EMPLOYING RESONANT LC NETWORK IN BASE-EMITTER CIRCUIT OFTRANSISTOR Filed April 15. 1964 APPLICANT Wilfred J. Jones Misegades 80Douglas ATTORNEYS United States Patent 3,359,430 PULSE GENERATOREMPLOYING RESONANT LC NETWORK IN BASE-EMITTER CIRCUIT OF TRANSISTORWilfred James Jones, Edinburgh, Scotland, assignor to The EnglishElectric Company Limited, London, England, a British company Filed Apr.15, 1964, Ser. No. 359,907 Claims priority, application Great Britain,Apr. 23, 1963, 15,960/ 63 3 Claims. (Cl. 307-88.5)

The invention relates to electric pulse generator circuits According tothe invention, an electric pulse generator circuit for producing anelectrical pulse of predetermined duration comprises a first transistorfor energization from a unidirectional voltage source, aninductance-capacitance timing circuit in the base-emitter circuit of thetransistor, means for momentarily changing the base-emitter potential ofthe transistor to alter the current in the collector circuit thereof toa new value, means inductively coupling the inductance-capacitancetiming circuit with the collector circuit whereby alteration of thecollector circuit current in response to a said momentary change ofbaseemitter potential causes the collector circuit current to be held atthe new value for a length of time dependent on the values of theelements in the inductance-capacitance timing circuit, and output meansoperative in response to the alteration of the collector current to thenew value for producing the said pulse, the pulse existing for the saidlength of time that the collector circuit current remains at the newvalue.

Preferably, the pulse generator circuit includes a load circuit in whichthe said pulse in the form of an electric current is to be produced, anda second transistor for controlling the current through the loadcircuit, the said output means comprising means for controlling thebaseemitter potential of the second transistor in dependence upon thecollector current of the first transistor.

Advantageously, the first transistor is normally conducting in a nearlysaturated condition and the said momentary alteration of itsbase-emitter potential renders it nonconducting.

According to a feature of the invention, the output means comprises achain of impedance elements for connection between the poles of theunidirectional source, the base of the second transistor being connectedto a point in the chain for determining the base-emitter potential ofthe second transistor, and means interconnecting the collector of thefirst transistor with the chain so that at least part of the collectorcircuit current of the first transistor passes through part of thechain, the said alteration in the collector circuit current of the firsttransistor thus varying the base-emitter potential of the secondtransistor. The part of the chain through which part of the collectorcircuit current of the first transistor flows may include an inductiveelement, so that alteration of the collector circuit current causes amagnified potential change across the inductive element, and a capacitorinterconnecting the inductive element and the base of the secondtransistor for transferring to the base the said magnified potentialcharge.

An electric pulse generator circuit for passing a current pulse ofpredetermined duration and magnitude through a load circuit, andincorporating the invention, will now be described by way of examplewith reference to the accompanying drawing which show the circuitschematically. The voltage waveforms at various points in the circuitare shown on the drawing, with the ground voltage (0) indicated and withpositive voltages upwards.

Referring to the drawing, a first transistor has its emitter-collectorcircuit connected between earth and a 3,359,430 Patented Dec. 19, 1967-10 v. busbar 11 through a resistor 12 and windings 13A, 13B of atransformer 13, the primary winding 13A being connected to the emitterand electrically in parallel with a capacitor 14, and the secondarywinding 13B to the collector. The base of the transistor 10 is connectedto a signal input terminal 15 through a diode 16, and to earth through adiode '17; it is also connected to the busbar 11 through a diode 18 andaresistor 19, both connected in series. A diode is connected between thecollector, of the transistor 10 and the junction of the resistor 19 andthe diode 18. r

sistor 28 with the inductor 29. The base of the second transistor isconnected to the junction of the resistor 26 with the diode 27 andthrough a capacitor 32 to point C. A diode 33 is connected between thecollector of the transistor 21 and the junction of the resistor 28 withthe diode 27.

The operation of the circuit will now be described. In the quiescentstate, current flowing through resistor 19 from the base-emitter circuitof transistor 10 holds the transistor conducting in a nearly saturatedcondition, the base-emitter potential of the transistor 10 not beingsufficient to cause diode 17 to conduct. The collector potential isprevented by the diode 20 from rising so close to the base potential asto cause the transistor to saturate: the maximum collector potential isabout 0.6 v. Thus the point C is maintained at this voltage while thetransistor 10 is conducting. The relative values of the resistors 26, 28and 30 are such that a proportion of the current in the resistor 30 ispart of the collector circuit current from the transistor 10 and passesthrough the diode 31 and the inductor 29. The relative values are alsosuch that the base of the transistor 21 is held positive so that thetransistor 21 is not conducting.

When a positive going pulse is applied to terminal 15 the transistor 10stops conducting and the consequent alteration of the current in thecollector circuit causes the current in the primary winding 13A of thetransformer 13 to be reversed. The capacitor 14 therefore charge so thatthe emitter potential of transistor 10 becomes negative with respect toits base potential and transistor 10 remains non-conducting for a perioddetermined by the capacitance of the capacitor 14 and the inductance ofthe primary winding 13A. At the start of this period, the collectorcurrent falls to zero and the current flow from transistor 10 to theresistor 30 ceases. The back E.M.F. across the inductor 29, which issetup by the cessation of current flow from transistor 10, lowers thepotential of the point C. This potential change has two effects:firstly, it is transferred through the capacitor 32 to the base of thetransistor 21, which starts to conduct; secondly, the current flowthrough the resistor 26, diode 27 and the resistor 28 is increased sothat the voltage drop across the resistor 26 is increased, thusmaintaining the transistor 21 conducting. The diode 33 prevents thetransistor 21 from saturating. When capacitor 14 has completelydischarged, at the end of the timing period, transistor 10 starts toconduct again. Its collector potential rises and this rise istransferred through diode 31 and capacitor 32 to the base of thetransistor 21 which becomes nonconducting. The potential of the point Crises near to the collector potential of the transistor 10, and thequiescent state is re-attained. Current from the collector of transistor10 divides between the path including resistor 12 and the path includingresistors 26, 28 and 30, and these resistors provide sufiicient dampingto prevent oscillation.

For the duration of the timing period, the length of which is determinedby the values of the capacitor 14 and the primary Winding 13A, thetransistor 21 is conducting and permits a current flow of predeterminedmagnitude to flow in the load circuit 23 for the duration of the timingperiod. The diode 17 prevents the base of transistor 10 from movingnegatively during the time transistor 10 is not conducting.

What I claim as my invention and desire to secure by Letters Patent is:

1. An electrical one-shot circuit having an active and a quiescentstate, comprising;

a transistor having emitter, base, and collector electrodes;

a collector circuit connected to the collector electrode and including afirst inductor and at least one resistor connected in series to a sourceof biasing potential; and

an emitter-base circuit connected between the emitter and baseelectrodes and including means for biasing the transistor intoconduction in the quiescent state, means for receiving input pulseseifective to turn the transistor OE and thereby cause the active stateto commence, and

a resonant circuit comprising a capacitor and a second inductorconnected in parallel:

the first and second inductors being inductively coupled together forcausing a reversal of current in the second inductor in response to achange of current in the first inductor occurring in consequence of aninput pulse.

2. An electrical one-shot circuit according to claim 1, in which theresonant circuit is connected to the emitter electrode of thetransistor.

3. An electrical one-shot circuit according to claim 1, and furthercomprising a transistorized inverter, and a diode connected between thecollector electrode of the transistor and the inverter and so poled asto become nonconductive during the active state of the circuit.

References Cited UNITED STATES PATENTS 2,952,784 9/1960 Carr 30788.53,002,110 9/1961 Hamilton 30788.5 3,040,185 6/1962 Horton 307--88.53,050,639 8/1962 Tate 307-885 3,229,151 1/1966 Attwood 30788.5

ARTHUR GAUSS, Primary Examiner.

J. S. HEYMAN, D. J. GALVIN, Assistant Examiners.

1. AN ELECTRICAL ONE-SHOT CIRCUIT HAVING AN ACTIVE AND A QUIESCENTSTATE, COMPRISING; A TRANSISTOR HAVING EMITTER, BASE, AND COLLECTORELECTRODES; A COLLECTOR CIRCUIT CONNECTED TO THE COLLECTOR ELECTRODE ANDINCLUDING A FIRST INDUCTOR AND AT LEAST ONE RESISTOR CONNECTED IN SERIESTO A SOURCE OF BIASING POTENTIAL; AND AN EMITTER-BASE CIRCUIT CONNECTEDBETWEEN THE EMITTER AND BASE ELECTRODES AND INCLUDING MEANS FOR BIASINGTHE TRANSISTOR INTO CONDUCTION IN THE QUIESCENT STATE, MEANS FORRECEIVING INPUT PULSES EFFECTIVE TO TURN THE TRANSISTOR OFF AND THEREBYCAUSE THE ACTIVE STATE TO COMMENCE, AND A RESONANT CIRCUIT COMPRISING ACAPACITOR AND A SECOND INDUCTOR CONNECTED IN PARALLEL: THE FIRST ANDSECOND INDUCTORS BEING INDUCTIVELY COUPLED TOGETHER FOR CAUSING AREVERSAL OF CURRENT IN THE SECOND INDUCTOR IN RESPONSE TO A CHANGE OFCURRENT IN THE FIRST INDUCTOR OCCURRING IN CONSEQUENCE OF AN INPUTPULSE.